AliceB, it's gonna just come down to using common sense. The ESL industry in Poland (can't speak for other countries, I only worked in Poland) is a sketchy scene but there are honest ones out there. Problem is the ones that are always hiring tend to be more high risk. I'd suggest looking for smaller schools, it'll be easier to keep tabs on the management and develop relationships. Also in my experience the smaller schools pay better (less overhead?) and go through less teachers. I worked for a big school in Wroclaw and we had about a 30 percent turnover each year.